Uveitis is responsible for approximately 30,000 cases of new legal blindness in the United States and 2.8-10% of all cases of blindness (1). Behets disease (BD) is a chronic relapsing multisystem inflammatory disorder of unknown etiology that is characterized by intraocular inflammation, oral and mucosal ulcerations, cutaneous lesions and inflammation that may affect other body organs such as the joints, intestinal tract, epididymis, blood vessels and the central nervous system (2). The need for a safer and more effective therapy for patients with ocular manifestations of BD refractory to or intolerant of systemic immunosuppressive therapy warrants further investigation. Reports define a specific role for interleukin (IL)-17A in the pathogenesis of Behets disease. This protocol will evaluate immune mediators including cytokine profiles (soluble and intracellular), lymphocyte phenotyping and regulatory T-cells in participants with BD. Epigenetic modifications will also be studied. Additionally, it has been suggested that American/Western BD patients may have different disease characteristics than their Mediterranean counterparts. The disease characteristics of American/Western and Mediterranean BD patients will be compared and evaluated. Blood samples from BD participants that have participated in other NIH protocols where participants consented for other or future use of samples has been obtained will be collected. In summary, the results will be analyzed with respect to disease in different ethnic groups, and clinical features of the disease (e.g., ocular vs. non-ocular involvement, active vs. quiescent disease). Additionally ocular and simulatenous blood/serum samples will be obtained from BD patients in Istanbul by our collaborator and wil be studied for intra-ocular microbiome. Anonymous blood samples (matched for race, age and sex) will be obtained from the NIH clinical center (CC) blood bank and will be compared to the diseased samples.